It is known that an aircraft, in particular a modern civil transport plane, has several control computers intended to make possible the automation of certain aircraft control and/or navigation tasks. Among these computers, we could mention in particular the FMS type (Flight Management System, in English) flight management computers, the OANS type (On-board Airport Navigation System, in English) airport navigation computers, the ADIRS type (Air Data Inertial Reference System, in English) computers able to supply aircraft position information, as well as environment surveillance computers. The latter provide, in particular, land proximity warning functions of the following types: GPWS (Ground Proximity Warning System, in English), EGPWS (Enhanced Ground Proximity Warning System, in English) or TAWS (Terrain Awareness and Warning System, in English), and warning functions of the TCAS type (Traffic alert and Collision Avoidance System, in English) about the risk of collision with another aircraft, radar surveillance, etc. Several of said functions can be grouped in an AESS type (Aircraft Environment Surveillance System) environment surveillance computer. These various computers contain each at least one aeronautical data base. For example, an OANS type computer has a data base containing at least airport mapping information, an AESS type computer has a data base that contains at least information about land topography, etc. Each computer has a storage capacity able to store said data base(s) of said computer. The storage capacity is defined when the computer is designed. This capacity is selected as a function of the number of entries contained in said data base(s), plus a margin that makes it possible to increase said number of entries in the future. This margin is, in general, determined as a function of the increase projections of said number of entries, and as a function of the storage capacity of the memories available when the computer is designed. However, the experience shows that the increase in said number of entries is often higher than expected and after several years, the storage capacity of said memory may prove to be insufficient to receive the complete data base(s). Since the control computers are computers on-board an aircraft, they must be subjected to certification by the competent authorities (FAA in the United States, JAA in Europe, etc.) and therefore it is hard to consider modifying the storage capacity of said memory for a specific computer, due to certification restrictions. In addition, a modification of the memories of the control computers would be complex and costly to implement on the entire fleet of aircrafts. Consequently, it would be necessary to adopt costly data filtering operations to limit the data base(s) to the strictly necessary data.
In addition, some of said control computers use specific data base formats, defined by each computer manufacturer. When the data bases are updated, the airlines must acquire updated data bases exclusively from the manufacturers of said computers. This leads to high update costs, due to the lack of competition.
Moreover, since the information contained in the various data bases intervenes in the aeronautic operations, the airlines must have the competent authorities certify their processes for ground processing of the updates for each of said data bases. For each data base, it is necessary to prove that the quality level of ground processing is higher than a minimum quality level, which is very expensive. The higher the number of control computers containing data bases, the more expensive.
On the other hand, the various data bases must be updated frequently (every 28 days for some data bases) for the entire fleet of each airline. In general, an airline only has a few days to perform the updates on all the aircrafts in its fleet. Consequently, each airline has very little time to perform the data base updates. Therefore, the time to load the updates in the various computers is critical, especially as the number of entries in each data base is very high. When an airline receives from its suppliers the updates for the various data bases, it performs a verification of the quality of the data contained in these updates. When a problem is detected, this makes the time for recharging the data bases in the various control computers even more critical.
Certain information must be used by several of said control computers. Consequently, they must be included in the corresponding data bases for each of the computers concerned. For example, information corresponding to the position of a landing runway threshold is used by the computers of the FMS type, the OANS type and the AESS type. Consequently, it must be duplicated in the data bases of the three above-mentioned computer types. Besides the use of the memory of said computers, duplicating this information can pose a risk of incoherence between the values of said entries used by various computers, if the corresponding data bases erroneously contain different values for some of said entries.